A cyclone separator of the kind mentioned at the outset is used in a suction cleaning appliance, in particular, a spray extraction appliance or a wet vacuum cleaner to separate the mixture of dirty cleaning liquid and suction air from each other. For this purpose, the mixture usually flows tangentially into the separating container, which is usually of cylindrical configuration, so that an annular flow forms in its interior. Owing to the suction extraction line extending into the interior, via which the interior can be subjected to negative pressure, the annular flow runs helically or spirally and, for this reason, is referred to as cyclone. Under the centrifugal action of the cyclone, cleaning liquid and dirt particles contained therein are hurled against the inner wall of the separating container. Under the influence of a wall boundary layer flow forming at the inner wall and under the influence of gravity, the cleaning liquid with the dirt particles can flow into a reservoir at the bottom of the separating container. The reservoir can be divided off from the remaining interior of the separating container by a partition wall provided with openings, for example, an intermediate bottom, in order to prevent separated cleaning liquid from being drawn by suction out of the reservoir. In order that cleaning liquid which has been drawn by suction into the interior will not be drawn out directly by suction through the outlet, the partition wall is provided in the direct direction of flow from the inlet to the outlet. The partition wall usually surrounds the outlet cylindrically, and the cyclone forms between the partition wall and the inner wall.
It may, however, happen that drops of liquid collect on the partition wall or a film of cleaning liquid forms on the partition wall. This is, for example, due to a short circuit of the flow in the separating container owing to back-up of the flow with a fluctuating charge of cleaning liquid or a fluctuating opening cross section of a connected suction nozzle, as a result of which the pressure conditions change in the separating container. Furthermore, wall friction of the mixture of cleaning liquid and suction air results in a boundary layer flow, the so-called “lid boundary layer flow”, which may form across a cover wall of the separating container up to the partition wall. This, in turn, results in a flow occurring around the free rim of the partition wall. Consequently, owing to the suction action exceeding the centrifugal force, liquid droplets are not separated off in spite of the presence of the partition wall, but are drawn off by suction through the outlet. To avoid this known problem, EP 1 736 089 A2 proposes configuring the partition wall in the shape of a bell and at the same time providing at the free rim a lateral window of approximately 90° in the circumferential direction of the suction extraction line. Such a construction of the partition wall is to enable the cleaning liquid to flow around the free rim of the partition wall in the direction of the suction extraction line, but then to rotate as a result of the cyclone and to be discharged through the window tangentially onto the inner wall. However, the cyclone separator described in EP 1 736 089 A2 is of relatively complicated construction and not inconsiderable size.
A further cyclone separator of the kind mentioned at the outset is described in EP 1 535 560 A2.
An object underlying the present invention is to provide a generic cyclone separator with which cleaning liquid can be reliably separated, while achieving a compact construction.